The field of data communications typically uses a modem to convey information from one location to another. Digital Subscriber Line (DSL) technology now enables modems to communicate rapidly large amounts of data. Modems communicate by modulating a baseband signal carrying digital data, converting the modulated digital data signal to an analog signal, and transmitting the analog signal over a conventional copper wire pair using techniques that are known in the art. These known techniques include mapping the information to be transmitted into a signal space constellation, and various coding and equalization techniques. The constellation can include both analog and digital information or only digital information.
In the above mentioned communications system, both digital data and an analog signal can be transmitted. The data signal to be transmitted is represented by a sequence of data symbols, where each data symbol is associated with a particular N-dimensional signal point value taken from a signal space. Similarly, the analog signal, which is represented by a voice signal, is processed so that it is mapped into the N-dimensional signal space to provide a voice signal point. This voice signal point defines the magnitude and angle of a voice signal vector about the origin of the signal space. The data symbol and the voice vector are then added together to select a resultant N-dimensional signal point. These N-dimensional signal points are grouped into signal space constellations and then transmitted to a far-end modem.
Upon reception of the transmitted N-dimensional signal point, the receiver of the far-end modem detects the embedded data symbol and subtracts the data symbol from the received N-dimensional signal point to yield the voice signal vector. This voice signal vector is then used to recreate the voice signal.
In the above mentioned communications environment, a control modem is located at a telephone company central office location. Connected to the control modem via a conventional copper wire pair are a plurality of remote modems. The remote modems reside at a common location, such as a residence or a business location. The communication technique between the control modem and the remote modems is generally half duplex. This means that only the control modem or one of the remote modems may transmit at any time. While one modem is transmitting, the other modems, whether the control modem or one of the remote modems cannot transmit. This predicament compromises line efficiency and prevents it from reaching near 100%.